can you tell sex by 7 weeks?

[hale moa]

I have 3 banty cochins that are now 7 weeks old. I cant see any real differences in them, but one is much smaller, has been from the first day, feathered out much slower.( they were all in a big bin at the feed store) none seem to have any difference in their combs, none have made any crowing attempts, could i be lucky enough to have picked 3 girls or are they still too young? i cant seem to figure out the picture posting.. mahalo, linnette

 

[tx_dane_mom]

i think it depends on the breeed, and I personally don't know bantanms, but i can tell on my rocks for instance around 2-3 weeks